Method and system for monitoring a hydrocarbon adsorber

ABSTRACT

A catalyst and method of forming the catalyst includes a catalyst body having hydrocarbon adsorber material and oxygen storage capacity material disposed thereon.

FIELD

The present disclosure relates to engine control systems, and moreparticularly to a system for monitoring a hydrocarbon adsorber.

BACKGROUND

The background description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description that may nototherwise qualify as prior art at the time of filing, are neitherexpressly nor impliedly admitted as prior art against the presentdisclosure.

Reduction of emission levels from internal combustion engines isincreasingly being regulated. Hydrocarbons are one example of aregulated exhaust gas constituent. Active hydrocarbon adsorbers are anemerging technology that may help vehicles meet the increasedregulations for exhaust gases. Typically, temperature sensors are usedto indicate the functionality of the hydrocarbon absorber. Thefunctionality check is a check of a bypass valve and of the thermal massof the substrate. Providing a functional check of the hydrocarbonadsorber may not meet future regulations due to the limited informationof a functional check.

SUMMARY

The engine control system according to the present disclosure provides amethod for determining the health of a hydrocarbon adsorber.

In one aspect of the disclosure, a method includes applying an oxygenstorage capacity material to a catalyst body and applying a hydrocarbonadsorber to the catalyst body.

In another aspect of the disclosure, a catalyst includes a catalyst bodyhaving hydrocarbon adsorber material and oxygen storage capacitymaterial disposed thereon.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 is a functional block diagram of an engine control systemaccording to the present disclosure;

FIG. 2 is a block diagram of the control module of FIG. 1;

FIG. 3 is flow diagram depicting a method for monitoring a hydrocarbonadsorber;

FIG. 4 is a flow diagram depicting a method for monitoring a bypassvalve associated with a hydrocarbon adsorber;

FIG. 5 is a plot of an upstream exhaust gas constituent sensor and adownstream exhaust gas constituent sensor where the adsorber has highexhaust gas constituent storage capacity;

FIG. 6 is a plot of an upstream exhaust gas constituent sensor and adownstream exhaust gas constituent sensor wherein the time between thesensor signals indicates low exhaust gas constituent storage capacity;

FIG. 7 is a cutaway view of a catalyst according to a first embodimentof the disclosure;

FIG. 8 is a cross-sectional view of a substrate according to a secondembodiment of the disclosure;

FIG. 9 is a cross-sectional view of a second substrate according to asecond embodiment of the disclosure;

FIG. 10 is a cutaway view of a catalyst according to a fourth embodimentof the disclosure;

FIG. 11 is a cutaway view of a catalyst according to a fifth embodimentof the disclosure; and

FIG. 12 is a flowchart of a method for forming a catalyst according tothe disclosure.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is in no wayintended to limit the disclosure, its application, or uses. For purposesof clarity, the same reference numbers will be used in the drawings toidentify similar elements. As used herein, the phrase at least one of A,B, and C should be construed to mean a logical (A or B or C), using anon-exclusive logical OR. It should be understood that steps within amethod may be executed in different order without altering theprinciples of the present disclosure.

As used herein, the term module refers to an Application SpecificIntegrated Circuit (ASIC), an electronic circuit, a processor (shared,dedicated, or group) and memory that execute one or more software orfirmware programs, a combinational logic circuit, and/or other suitablecomponents that provide the described functionality.

The following disclosure is set forth using an oxygen sensor formeasuring an exhaust gas constituent. However, other exhaust gasconstituents may also be measured to verify the functionality of thehydrocarbon adsorber. The present disclosure is applicable to bothactive and passive HC adsorbers.

Referring now to FIG. 1, an exhaust system 10 in communication with anengine 12 is illustrated. The exhaust system 10 includes a firstthree-way catalyst 14, an exhaust conduit 16, and a second three-waycatalyst 18. Exhaust gases from the engine 12 flow through an exhaustmanifold 20 and into the exhaust system 10.

A hydrocarbon adsorber 30 is disposed between the first three-waycatalyst 14 and the second three-way catalyst 18 within the exhaustconduit 16. The hydrocarbon adsorber 30 may be cylindrical in shapehaving a passage 32 therethrough. The passage 32 may be defined by achannel wall 34. A bypass valve 40 may be disposed within the passage32. By opening and closing the bypass valve 40, the exhaust gasesrepresented by arrow 42 may be directed through the passage 32 when openand thus substantially bypassing the hydrocarbon adsorber 30. When thebypass 40 is closed, blocking the passage 32, the hydrocarbon adsorber30 receives exhaust gases 42.

The hydrocarbon adsorber 30 has a first end 44 which may be referred toas an inlet or upstream end. The first end 44 is disposed to firstreceive the exhaust gases 42. Thus, the first end 44, the hydrocarbonadsorber 30 is disposed toward the first three-way catalyst 14 and theengine 12. The second end 46 of the hydrocarbon adsorber 30 is disposedtoward the outlet or downstream end of the exhaust conduit 16 toward thesecond three-way catalyst 18.

The hydrocarbon adsorber 30 may include material that has an exhaust gasconstituent storage capacity function. In this disclosure, the exhaustgas constituent is oxygen and the hydrocarbon adsorber includes anoxygen storage capacity function. Oxygen storage capacity (OSC) material(or element) 50 is illustrated as a box within the hydrocarbon adsorber44. However, the oxygen storage capacity material 50 may be disposedthroughout the hydrocarbon adsorber 30. The oxygen storage capacitymaterial 50 may have a thermal stability that degrades at a rate equalto or faster than that of the hydrocarbon adsorber 30. The oxygenstorage capacity of the adsorber catalyst is correlated to emissionperformance. The OSC material 50 provides an oxygen buffer. Thus, theoxygen storage of the oxygen storage material may be measured todetermine the health of the adsorber 30. Likewise, measurement of theoxygen storage capacity may allow for diagnostics of the functioning ofthe valve 40 in addition to the adsorber health. A lean-to-richtransition in the engine control and a time for changing the oxygenlevels can be used to determine the adsorber health.

A first exhaust gas constituent sensor 60 is disposed within the exhaustconduit 16 and generates a first exhaust gas constituent signalcorresponding to the exhaust gas constituent level within the exhaustconduit 16. In carrying forward with the present example, the exhaustgas constituent sensor may be an exhaust gas oxygen sensor.

An exhaust gas constituent sensor 62 may also be disposed within thehydrocarbon adsorber 30 to determine the level of storage of the exhaustgas constituent within the adsorber 30. Carrying forward with thepresent example, the exhaust gas constituent sensor 62 may be an oxygensensor that generates a signal corresponding to the exhaust gasconstituent within the hydrocarbon adsorber. The first exhaust gasconstituent signal from the sensor 60 and the second exhaust gasconstituent sensor signal from the exhaust gas sensor 62 arecommunicated to a control module 70. The control module 70 may also bein communication with the bypass valve 40 for controlling the openingand closing of the bypass valve. While the sensor 62 is illustratedwithin the adsorber, the sensor 62 may be located downstream of theadsorber such as before the TVVC 18 or after the TWC 18.

Referring now to FIG. 2, the control module 70 is illustrated in furtherdetail. Control module 70 includes an exhaust gas constituentdetermination module 102 that may be in communication with the sensor 60illustrated in FIG. 1. The exhaust gas constituent determination module102 determines an exhaust gas constituent level for a particular exhaustgas constituent such as oxygen within the exhaust stream.

An adsorber exhaust gas constituent determination module 104 determinesan amount of exhaust gas constituent within the adsorber. The sensor 62may generate a signal used by module 104. The exhaust gas constituentsignal from the exhaust gas constituent determination module 104 may becommunicated to an adsorber exhaust gas storage capacity determinationmodule 106. Again, the exhaust gas constituent storage capacity of theadsorber may be derived directly from the amount of exhaust gasconstituent measured in the module 104 or from a time associated with alean-to-rich transition as will be described below.

A comparison module 108 may receive the exhaust gas constituent signalfrom the exhaust gas constituent determination module 102. Thecomparison module 108 may receive the adsorber exhaust gas determinationmodule signal from the adsorber exhaust gas constituent determinationmodule 104 or the exhaust gas constituent storage capacity from theadsorber exhaust gas constituent storage capacity determination module106. By comparing the amount of exhaust gas constituent within theexhaust with either the constituent storage capacity or the amount ofexhaust gas stored within the adsorber, the comparison module maygenerate a fault at the fault indicator module 110. The comparisonmodule 108 may subtract the exhaust gas constituent measured in module102 with the exhaust gas constituent measured in module 104 and comparethe difference with a threshold. In comparison to the threshold, thefault indicator module 110 may be actuated. Likewise, the comparisonmodule 108 may also compare the exhaust gas constituent storage capacity106 with the amount of exhaust gas constituent within the exhaust gasfrom the module 102. When the amount of exhaust gas storage capacity hasbeen utilized by the exhaust gas constituent within the exhaust gas, theadsorber is operating properly. However, if an unexpected amount ofstorage capacity is available, the adsorber may not be functioningproperly and the fault indicator module 110 may indicate a fault. As canbe seen, a number of different methods may be determined based upon theexhaust gas constituent within the exhaust stream and the exhaust gasconstituent within the adsorber. At a minimum, a comparison between theamount of exhaust gas within the adsorber and the exhaust gas stream isperformed.

The comparison module 108 may also compare the time between alean-to-rich transition between the first sensor 60 and the secondsensor 62. If the time measured is greater than a time threshold thenthe adsorber is functioning properly (i.e., has enough oxygen storagecapacity).

A bypass valve operation module 112 may also be included within thecontrol module 70. The bypass valve operation module 112 may be incommunication with a change determination module 114. The changedetermination module may also receive signals from the exhaust gasconstituent determination module 102, the adsorber exhaust gasconstituent determination module 104, or the adsorber exhaust gasconstituent storage capacity determination module 106 or combinationsthereof. The change determination module 114 may determine a change inthe amount of exhaust gases or the amount of storage capacity of theexhaust gas constituent within the adsorber. The valve operation module112 may open and close the valve and a change in the amount ofconstituent gases stored within the adsorber may be determined. In asimilar manner to that described above, a difference between the amountof exhaust gases within the exhaust gas stream may be compared to theamount within an adsorber. This may be performed at two different times,including while the bypass valve is opened and closed. A differencebetween the opening and closing amounts of exhaust gases within theadsorber should be evident. If no change is evident, then the valve maynot be operating properly. This may be performed by subtracting orcomparing the closing and opening amount of constituent gases andcomparing the difference with a threshold. If the difference is notabove a threshold, the valve is not operating properly.

The fault indicator module 110 may be in communication with an on-boarddiagnostics (OBD) interface 116. The on-board diagnostics interface 116may provide an interface to the on-board diagnostics system that may belocated outside of the control module 70. The on-board diagnosticinterface may provide fault codes or other fault signals in response toerrors in the valve operation or in the adsorber.

Referring now to FIG. 3, a method of determining a fault of the adsorberis set forth. In step 210, the engine is operated. The diagnostic may beperformed during regular operation. However, the diagnostic may also beperformed during an enabling condition portion which may require theproduction of a certain amount of exhaust gas constituents in step 212.For example, the engine may be run in a rich condition, lean conditionor other controlled manner such as during a lean-to-rich transition.Other enabling conditions may include run time and the temperature ofthe adsorber. In step 214, a hydrocarbon adsorber performance monitoringstep is initiated. In step 216, the exhaust gas constituent level in theexhaust system is determined. This may be performed using the exhaustgas sensor 60 illustrated in FIG. 1. The time of a transition may berecorded. In step 218, the control valve may be closed. In step 220, theexhaust gas constituent level in the adsorber is determined. In step222, if the exhaust gas constituent corresponds to an adequate capacity,step 224 switches the air fuel ratio from lean to rich. Step 226determines the exhaust gas constituent storage capacity within theadsorber. This is directly determined from the exhaust gas constituentlevel from step 220. In step 228, a minimum allowable OSC capacity maybe determined. In step 230, the measured exhaust gas constituent leveland the exhaust gas constituent storage capacity are compared. Thecomparison is performed between the exhaust gas constituent level instep 220 and the storage capacity from step 226. In step 232, if themeasured exhaust gas constituent level is less than a minimum exhaustgas constituent storage capacity, control proceeds to step 234 togenerate a fault signal. The fault signal may be an audible fault signalor a visual fault signal. The fault signal may also be a fault signalstored within the on-board diagnostic system. When the minimum storagecapacity is exceeded, step 210 is again performed.

As mentioned above, the actual exhaust gas constituent storage capacitymay be determined directly from the oxygen sensor signals or by a timebetween the transition between the first oxygen sensor 60 and the secondoxygen sensor 62. Thus, when the two times are subtracted, a timedifference period may be determined and compared to a time differencethreshold for determining the oxygen storage capacity. For example, whenthe time between the transition is short, the oxygen storage capacity ofthe adsorber is low but when the time between the transition is high orabove a threshold, the adsorber may include enough oxygen storagecapacity.

Referring now to FIG. 4, a method similar to that described above withrespect to FIG. 3 is set forth. In step 310, the engine may be operatedin a particular way. As mentioned above, engine operation may bedifferent than that for FIG. 3 in which the adsorber is tested. In thefollowing method, the bypass valve is tested for functionality. Again,the engine may be operated in a particular way such as in a rich mode,lean mode, or a combination of both.

In step 320, a bypass valve monitoring mode is entered. In step 322, theexhaust gas constituent level may be determined from the exhaust gasconstituent sensor 60 of FIG. 1. This step is similar to step 222 ofFIG. 3. Step 324 determines the exhaust gas constituent level in theadsorber. This step is similar to that of step 224 of FIG. 3. In step326, the exhaust gas constituent storage capacity of the adsorber isdetermined. This is similar to step 226 described above in FIG. 3. Itshould be noted that one or all of the steps 322-326 may be performed todetermine whether or not the bypass valve is operating properly. Also,steps 322-326 may be determined at different times such as when thebypass valve is expected to be open and when the bypass valve isexpected to be closed under the control of the control module 70. Instep 328, the exhaust gas constituent level and the exhaust gasconstituent storage capacity may be compared. Again, this is an optionalstep depending on the type of monitoring chosen.

In step 330, the change in the exhaust gas constituent storage capacityof the adsorber or whether the exhaust gas constituent corresponds to anexhaust gas constituent storage capacity may be determined in step 330.If no change in the exhaust gas constituent storage capacity is achievedwhen the valve is opened and closed or the exhaust gas constituent doesnot correspond to an exhaust gas constituent storage capacity, a faultis generated in step 332. If the exhaust gas constituent does correspondto the exhaust gas constituent storage capacity, step 310 may be againperformed where the engine is operated until bypass valve functioning isdetermined.

Referring now to FIG. 5, the output of the upstream oxygen sensor(pre-O₂ sensor) and the downstream or post-O₂ sensor is illustrated.During a first time period T1, the engine is operatedstoichiometrically, resulting in an undefined amount of oxygen storedwithin the adsorber. During time period T2, the engine is operated in alean state. This allows the adsorber capacity determination to start offat a pre-determined reference level. Between time period T2 and T3, alean-to-rich transition is performed. The time between the T2-T3transition and T4 corresponds to the time period T3 which corresponds tothe oxygen storage capacity of the adsorber. Thus, a time of thetransition between the pre or upstream oxygen sensor transition and thedownstream oxygen sensor transition provides the time T3 which directlycorresponds to the oxygen storage capacity of the adsorber. It should benoted that operating in a rich state then switching from a rich to leanstate may also be used. Running in a rich state will fully deplete theOSC material to a known amount. Either way should be consideredequivalents and can performed using the teachings herein.

Referring now to FIG. 6, the time periods T1 and T2 correspond directlyto those illustrated in FIG. 5 and, thus, will not be described further.However, the time period between T5 and T6 is small compared to the timeperiod T3 illustrated in FIG. 5. This small indication of the oxygenstorage capacity may indicate that the oxygen storage capacity of theadsorber is reduced and, thus, the adsorber is not operating properly.

Referring now to FIG. 7, a cutaway view of catalyst 410 is illustrated.The catalyst 410 may be annular in cross-section so that the bypass 32is formed therethrough. The catalyst 410 includes a catalyst body 412.The catalyst body 412 may have a washcoat thereon. The washcoat mayinclude hydrocarbon (HC) adsorbant material 414 such as zeolite. Thehydrocarbon adsorbant material 414 may be applied with the washcoat.

An oxygen storage capacity (OSC) material (or element) 416 may also bedisposed on the substrate body 412. The substrate body 412 may includethe OSC material 416 within the washcoat. The oxygen storage capacitymaterial may be cerium oxide (CeO₂). The OSC material 416 may bedesigned to degrade at a rate greater than or equal to the zeolitematerial within the HC adsorbant material 414. Both the hydrocarbonadsorbant material 414 and the oxygen storage capacity material 416 maybe applied using a washcoat. The washcoat may apply the hydrocarbonadsorbant material in a uniform layer interspersed with the oxygenstorage capacity material 416. The oxygen storage capacity material maybe a high surface area cerium oxide particles that are less than 15nanometers in size. The surface area of the particles may be over 100m²/g. Trace amounts of metal such as gold, copper, silver or platinummay also be included within the oxygen storage capacity material. Theconcentrations may be at 1 g/ft³. The additional trace metals mayenhance the oxygen storage capacity of the cerium oxide. The oxygenstorage capacity material is matched to the deactivation temperatures ofthe hydrocarbon adsorber materials. The materials may be modified by theaddition or deletion of trace amounts of specific metals to alter thetemperature ranges where deactivation occurs. The alteration of thetemperatures may be performed for various configurations as required bythe design process. By using the materials in the adsorber washcoat,emissions correlated diagnostics may be performed as described above. Asillustrated above in FIG. 1, pre- and post-oxygen or lambda sensors maybe used to measure the oxygen storage which may be used to correlate thehydrocarbon emissions and oxygen storage.

Referring now to FIG. 8, one method for forming a catalyst 410′ includesa substrate 450 that has a first layer 452 disposed on each sidethereon. The first layer 452 includes an oxygen storage capacitymaterial. A second layer 454 is disposed on the first layer 452. Thesecond layer 454 includes a hydrocarbon adsorber material. Both theoxygen storage capacity material and the hydrocarbon adsorber materialare described above.

The oxygen storage capacity material may improve resistance tohydrocarbon fouling, coking or catalyst poisoning.

Referring now to FIG. 9, an embodiment similar to that illustrated inFIG. 8 is illustrated. In this example, the catalyst 410″ includes asubstrate 450 as illustrated above. In this example, an HC adsorbercoating 462 is applied to each side of the substrate 450. An oxygenstorage capacity layer 464 is applied to each HC adsorber coatingmaterial layer.

Referring now to FIG. 10, the catalyst 410″′ is illustrated having ahydrocarbon adsorber material 470 disposed within a washcoat. Anovercoat or zone coat 472 disposed toward the front or exhaust-receivingportion (toward the engine) of the catalyst body 474 is illustrated.This allows the oxygen storage capacity material to be disposed in alocation as required. The zone coat 472 may be applied after thewashcoat.

Referring now to FIG. 11, an oxygen storage capacity zone 490 isillustrated toward the rear or outlet portion of the catalyst 410″″. Inthis embodiment the increased oxygen storage capacity may be placedtoward the rear of the catalyst 410″″ (toward a tail pipe).

Referring now to FIG. 12, a method for forming a catalyst is set forth.In step 510, an annular substrate is provided. The annular substrate isformed so that a bypass channel 32 is formed therein. In step 512,oxygen storage capacity material is applied to the substrate. The oxygenstorage capacity material may be applied in a washcoat or in zones onthe substrate material.

In step 514, hydrocarbon adsorbant material is also applied to thesubstrate. Both the hydrocarbon adsorbant material and the oxygenstorage capacity material may be applied simultaneously within awashcoat. Further, the hydrocarbon adsorbant material may be applied tothe substrate prior to the oxygen storage capacity material or after theapplication of oxygen storage capacity material.

After the hydrocarbon adsorbant material and the oxygen storage capacitymaterial are applied to the substrate, the catalyst is used in thediagnostic method as described above.

Those skilled in the art can now appreciate from the foregoingdescription that the broad teachings of the present disclosure can beimplemented in a variety of forms. Therefore, while this disclosure hasbeen described in connection with particular examples thereof, the truescope of the disclosure should not be so limited since othermodifications will become apparent to the skilled practitioner upon astudy of the drawings, the specification and the following claims.

What is claimed is:
 1. A system comprising: a catalyst body configuredto receive an exhaust gas from an engine; a hydrocarbon adsorberdisposed on or within the catalyst body, wherein the hydrocarbonadsorber is configured to have a first degradation rate at temperaturesgreater than a predetermined temperature at which the adsorber begins todegrade; and an oxygen storage element disposed on or within thecatalyst body, wherein the oxygen storage element comprises oxygenstorage material, wherein the oxygen storage material is configured tohave a second degradation rate at the temperatures greater than thepredetermined temperature, and wherein the second degradation rate isgreater than or equal to the first degradation rate.
 2. A system asrecited in claim 1, wherein the hydrocarbon adsorber and the oxygenstorage element are disposed within a washcoat of the catalyst body. 3.A system as recited in claim 2, wherein the catalyst body comprises asubstrate, wherein the washcoat is disposed on the substrate.
 4. Asystem as recited in claim 3, further comprising: a first layer disposeddirectly on the substrate; and a second layer disposed on the firstlayer.
 5. A system as recited in claim 4, wherein: the first layercomprises the hydrocarbon adsorber; and the second layer comprises theoxygen storage element.
 6. A system as recited in claim 4, wherein: thefirst layer comprises the oxygen storage element; and the second layercomprises the hydrocarbon adsorber.
 7. A system as recited in claim 3,wherein the hydrocarbon adsorber is disposed on an inlet portion of thecatalyst body and upstream from the oxygen storage element.
 8. A systemas recited in claim 3, wherein the oxygen storage material comprisescerium oxide (CeO₂), wherein the CeO₂ is dispersed uniformly within thewashcoat.
 9. A system as recited in claim 1, wherein the oxygen storagematerial is dispersed non-uniformly within a washcoat of the catalystbody.
 10. A system as recited in claim 1, wherein the oxygen storagematerial is disposed on an outlet portion of the catalyst body anddownstream from the hydrocarbon adsorber.
 11. A system as recited inclaim 1, wherein the catalyst body has an annular cross section.
 12. Asystem as recited in claim 1, wherein: the hydrocarbon adsorbercomprises zeolite; and the oxygen storage material comprises ceriumoxide and degrades at a rate faster than or equal to the zeolite.
 13. Asystem as recited in claim 1, wherein the oxygen storage material:comprises particles; each of the particles has a surface area of a sizeless than a first predetermined surface area; and the surface area, ofthe particles as disposed on or within the catalyst body, is greaterthan a second predetermined surface area per a predetermined number ofgrams of the particles.
 14. A system as recited in claim 1, wherein: theoxygen storage element comprises metal elements; and a concentration ofthe metal elements in the catalyst body is less than a predeterminednumber of grams per cubic foot.
 15. A system as recited in claim 14,wherein the metal elements comprise at least one of copper, gold, silverand platinum.
 16. A system as recited in claim 14, wherein: theconcentration of the metal elements is set such that a deactivationtemperature of the oxygen storage element is matched to a deactivationtemperature of the hydrocarbon adsorber; and the deactivationtemperature of the hydrocarbon adsorber is a temperature above whichperformance of the hydrocarbon adsorber begins to degrade.
 17. A systemas recited in claim 1, wherein the hydrocarbon adsorber and the oxygenstorage element begin to degrade at the predetermined temperature.
 18. Asystem as recited in claim 1, further comprising: a first constituentdetermination module that determines an oxygen level within the exhaustgas; a second constituent determination module that determines an amountof exhaust gas constituent within the hydrocarbon adsorber; a storagecapacity module that determines a storage capacity of the hydrocarbonadsorber based on the amount of exhaust gas constituent within thehydrocarbon adsorber or a time period associated with a lean-to-richtransition of an air fuel ratio of the engine; and a comparison modulethat generates a fault signal based on the oxygen level within theexhaust gas and at least one of the amount of exhaust gas constituentwithin the hydrocarbon adsorber and the storage capacity, wherein thefault signal indicates that the storage capacity of the hydrocarbonadsorber is less than a minimum storage capacity.
 19. A system asrecited in claim 18, further comprising: a first sensor positionedupstream from the catalyst body, wherein the first sensor generates afirst signal indicative of the oxygen level within the exhaust gas; anda second sensor connected to the catalyst body, wherein the secondsensor generates a second signal indicative of the amount of exhaust gasconstituent in the hydrocarbon adsorber, wherein the first constituentdetermination module determines the oxygen level within the exhaust gasbased on the first signal, and wherein the second constituentdetermination module determines the amount of exhaust gas constituent inthe hydrocarbon adsorber based on the second signal.
 20. A system asrecited in claim 19, wherein: the storage capacity module determines thestorage capacity of the hydrocarbon adsorber based on the time periodassociated with a lean-to-rich transition of the air fuel ratio of theengine; and the time period associated with the lean-to-rich transitionstarts when the first sensor transitions from indicating a lean mode toindicating a rich mode, and ends when the second sensor transitions fromindicating a lean mode to indicating a rich mode.
 21. A system asrecited in claim 18, wherein: the second constituent determinationmodule determines an oxygen level within the hydrocarbon adsorber; thestorage capacity module that determines an oxygen storage capacity ofthe hydrocarbon adsorber based on the oxygen level within thehydrocarbon adsorber or the time period associated with the lean-to-richtransition of the air fuel ratio of the engine; the comparison modulethat generates the fault signal based on the oxygen level within theexhaust gas and at least one of the oxygen level within the hydrocarbonadsorber and the oxygen storage capacity; and the fault signal indicatesthat the oxygen storage capacity of the hydrocarbon adsorber is lessthan a minimum oxygen storage capacity.